Abrasive articles and method of making abrasive articles



Nov. 29, 1966 J- ABERNATHY 3,287,862

ABRASIVE ARTICLES AND METHOD OF MAKING ABRASIVE ARTICLES Filed NOV. 50, 1964 William J.Aberna1hy,

INVENTOR.

ATTORNEY.

United States Patent 3,287,862 ABRASIVE ARTICLES AND METHOD OF MAKING ABRASIVE ARTICLES William J. Abernathy, 209 Cole Drive, S.E., Huntsville, Ala. Filed Nov. 30, 1964, Ser. No. 414,830 8 Claims. (Cl. 51-204) This invention relates to the general field of abrasive machining and particularly to lapping plates, abrasive surfaced articles and methods for making the same, and this application is a continuation in part of my copending application of the same title, Serial No. 350,084 filed March 6, 1964.

In one area of abrasive machining, which is termed lapping, the goal is to produce smooth and accurate surfaces. The abrasive supporting member used in such work is termed a lap, lapping plate or lapping carrier, which terms shall be used herein interchangeably. Lapping plates are usually made of fairly soft and porous materials such as cast-iron, copper, brass, and lead. Some are made of granite. Lapping plates become abrasive articles or laps when they are combined with an abrasive which is charged or rolled into the surface of the plates. Examples of abrasives so combined are: emery flour, diamond dust, silicon carbide and aluminum oxide. Abrasive articles as contemplated herein, of the lapping variety and of the type used in more coarse work, may take an unlimited number of configurations, depending only upon the contour of the article to be machined.

There are two major faults with the abrasive articles described above insofar as they are lapping devices. First, a lapping device is only useful so long as it retains its contour to a very precise degree, within a few microinches, and experience indicates that with the known types of lapping devices referred to above useful life, before refinishing is necessary, is often quite short. Second, galling or scratching of articles being lapped is a common occurrence.

Another approach to the construction of abrasive laps, apparently employed to a very limited extent and for special uses, is to bond the abrasive to the lapping plate or supporting structure. This same approach is widely applied to less precision abrasive machining devices such as abrasive wheels for grinding. The diificul-ty, of course, is to find a bonding agent that will hold the abrasive grits in place. Particularly is this so where severe temperature and pressure conditions are experienced. In an effort to find a bonding agent equal to the job many types have been employed and they include; silicate, vitrified, shellac, rubber, resinoid, and certain metal bondings. None have been found which provide a factor of durability approaching that of the extremely hard abrasives, such as diamond, which they must :hold in place. In other words the bonding or holding agent is the weak link in the structure. This is also true with the lapping plates described in the preceding paragraph wherein wear and galling are the difiiciencies.

It is the object of this invention to overcome the aforesaid difilculties and to provide a basic advance in the art of abrasive machining.

The attached drawing forming a part of this specification is a pictorial view, partly in section, of an embodiment of this invention.

In accordance with the invention an abrasive supporting member 10 is cut or formed of an anodizable stock material such as aluminum. The working surface on surfaces 12 are then machined or finished to the degree of finish determined by the requirements for use of the end product. Where the use is to be lapping and thus the end product a lapping plate the working surfaces are lapped to a 4 to 6 microinch finish. For extreme precision work the stock material is then stress relieved in accordance with standard techniques which comprise first elevating the temperature ofthe material substantially above room temperature and then lowering it substantially below room temperature. After this, the surfaces are relapped to the prior 4 to 6 microinch finish. At this point, in accordance with one aspect of the invention, an abrasive grit 14 is charged that is pressed, air blasted,

shot, or rolled into the working surfaces 12 of the supporting member.

Next, the working surfaces are anodized, or hard anodized, to form a hard anodic coating 16 of a maximum obtainable thickness, or less, depending upon the grit size of abrasive employed. With the smaller grit sizes, e.g. which may go down to a fraction of a micron, coatings substantially thinner than .001 inch may be used. The grits of the abrasive are held by the anodic coating to a degree of bonding believed never to have been previously achieved. For maximum cutting efficiency the surfaces prepared in this manner should be polished or otherwise treated to recess the anodic coating slightly with respect to the abrasive grits. One method is to buff or polish it using felt and an abrasive grit wherein the grit size is smaller than that originally charged into the surfaces prior to anodizing.

In accordance with another feature of the invention an additional step in the process is inserted to provide still improved bonding security. After the grit is impressed in the surface as aforesaid and before anodizing, the charged anodizable surface, e.g. of aluminum, is coated, as by depositing technics or by use of a metalizing gun, with a thin coating of the same or a compatible anodizable material. By means of this step, cavities which remain around grit due to the working back and forth of grit when rolled or worked into the surface are filled prior to anodizing. This step is, of course, important when the cavities to be filled are larger than are filled by the anodizing step, which depends, in part, on the anodizing thickness being used or obtainable.

In accordance with still another feature of the invention layers of abrasive are achieved by repeating the steps of the process set forth above with a metal coating step, as aforesaid, inserted after each instance of anodizing.

By this process, thicker and longer wearing abrasive devices, such as employed in cutting and grinding may be manufactured. The modified process requires that after anodizing, the surface would be metalized, or otherwise coated with a compatible anodizable surface; then the new surface would be recharged with abrasive grit as foresaid and reanodized. This process is repeated until the desired overall thickness of abrasive material is obtained. Alternatively, for the reasons stated above, the additional step of metal coating may be inserted between each charging step and anodizing step.

As is perhaps clear the anodic bonding technique is equally applicable to the construction of fine cutting devices such as abrasive laps and to the construction of coarse cutting devices such as abrasive saws, grinding wheels and the like. Abrasive grit size is chosen in terms of the character of the abrasive cut desired.

Within the normal range of diamond abrasive grits employed, anodic bonding is believed to be the most effective bonding discovered for holding such abrasive grits, and vastly superior to the techniques cited above.

It is, of course, to be understood that in the construction of coarse accuracy devices that the steps outlined above relating to precision working of the anodizable material, Where a lapping device was the end product, may be omitted.

With respect to all of the forms of articles constructed in accordance with the methods set forth above it can be clearly stated that new standards of performance and durability have been achieved. In view of the harder surfaces and abrasive holding and bonding characteristics provided, greater pressures and thus cutting speeds can be obtained. Further, and of extreme significance is the fact that a much cooler operation of cutting and grinding is achieved. Galling of work due to scoring of lapping plates has been essentially eliminated and they are much easier to clean than conventional plates. Also, light metals, such as aluminum are used for abrasive tools rather than heavier materials such as cast iron, a distinct advantage in many instances.

Other uses of my invention will no doubt be appreciated by those skilled in the art and accordingly I do not wish to be limited except by the scope of the accompanying claims.

I claim: a

1. The method of making an abrasive article comprising:

(A) preparing from anodizable stock material a surface conforming to a desired contour;

(B) charging said surface with an abrasive grit;

(C) anodizing said surface wherein said abrasive grit is a harder material than the anodic coating resulting from anodizing said surface.

2. The method set forth in claim 1, and including the further and subsequent step of lapping said surface while employing a second abrasive grit, said second abrasive grit being of smaller dimension particlesthan said first named abrasive grit.

3. The method set forth in claim 2, wherein said anodizable stock material is aluminum.

4. An abrasive article comprising:

(A) a supporting base comprising a material capable of being anodized and being aluminum;

(B) an anodized coating on a surface of said base;

(C) a plurality of abrasive grits of diamond material positioned to form an abrasive surface conforming to said surface of said base; and

(D) said abrasive grits being bonded together by said anodized coating.

5. The method of making an abrasive article of successive layers wherein the making of each layer com prises the steps:

(A) forming from :anodizable stock material a surface conforming to a desired contour;

(B) charging said surface with an abrasive grit;

(C) anodizing said surface; and

applying to the resulting anodized surface of each intermediate layer a thin coating of anodizable material to provide a charging surface for the next layer.

6. The method of making an abrasive article set forth in claim 5, comprising the further step of applying an additional thin coating of anodizable material to each layer between said steps (B) and (C).

7. An abrasive article comprising a plurality of layers wherein each successive layer comprises:

(A) a surface of material capable of being anodized;

(B) an anodized coating on said surface;

(C) a plurality of abrasive grits positioned to form an abrasive contour conforming to said surface; and

(D) said abrasive grit being bonded together by said anodized coating.

8. The abrasive article set forth in claim 7, further comprising a thin coating of anodizable material coating said abrasive grits and said surface of at least one of said layers, said thin coating being immediately under a said anodized coating.

References Cited by the Examiner UNITED STATES PATENTS- 2,585,128 2/1952 Howe et al 20438.l X 2,798,037- 7/ 1957 Robinson 204-58 X FOREIGN PATENTS 656,566 2/1938 Germany.

ROBERT C. RIORDON, Primary Examiner.

L. S. SELMAN, Assistant Examiner. 

4. AN ABRASIVE ARTICLE COMPRISING: (A) A SUPPORTING BASE COMPRISING A MATERIAL CAPABLE OF BEING ANODIZED AND BEING ALUMINUM; (B) AN ANODIZED COATING ON A SURFACE OF SAID BASE; (C) A PLUALITY OF ABRASIVE GRITS OF DIAMOND MATERIAL POSITIONED TO FORM AN ABRASIVE SURFACE CONFORMING TO SAID SURFACE OF SAID BASE; AND (D) SAID ABRASIVE GRIFTS BEING BONDED TOGETHER BY SAID ANODIZED COATING. 